The problem of the present invention is to minimize the scrap when manufacturing packages, especially packages having qualified barrier characteristics, for instance of the quality required for full conserves.
According to a specific embodiment of the invention, the problem of the invention is to make the total procedure, from plastics granulate to a finished packing container, waste or scrap-free, starting out from so called "scrap-free" thermoforming technique.
The general problem of minimizing waste has, of course, been dealt with before and it is known to extrude an extrudate in pipe form and laminate such pipe by a barrier material.
In the Swedish patent No. 751017069 (same as U.S. Pat. No. 4,484,968) there is shown a method of applying a barrier laminate cross-wise an extruded pipe.
According to another method, described in Swedish patent application No. 850170160, the starting point is a profile, which may be solid or hollow, and strips are applied in the longitudinal direction of the profile.
In the first mentioned case, where the extrudate is a hollow extrudate, and in the last mentioned case, when the extrudate is a hollow profile, there if obtained an absolutely scrap free manufacture of the "supporting container" casing requiring the largest amount of material, i.e. the seamless inner layer.
That, which has been said, is one of the reasons for making extrusion of hollow profiles a most competitive approach to the package manufacturing technique. The dimension of the extrudate defines exactly the dimension of the casing of the container without any need for scrap introducing working, for instance edge cutting. However, according to one embodiment of the present invention further working includes a thermo forming process of the so called scrap-free type.
According to prior art, webs obtained by planar extrusion of plastics through a straight orfice onto a mould roller, in contrary to the cut profile of the present invention, obtain marginal regions which do not meet the stipulated tolerances, implying that such marginal regions have to be removed as waste material, for instance by roller cutting.
However, when extruding pipes and cutting such into casings, the transport volume, from the manufacturing place of the casings and the packages to the filling place, if said locations are geografically separate, will be pretty large and "air containing".
The prior art lamination operations are carried out against a support which perhaps does not always provide a sufficient pressure for lamination, meaning there is a risk for air bubbles and an inferior end product.
In certain cases the prior art lamination methods do also imply problems with matching the print of the package.